The present invention relates to a pushbar-type ratchet wrench, and more particularly to a push bar-type ratchet wrench in which the detent section of the push bar is engaged with the ratchet at a higher position for increasing the torque strength and operation sensitivity thereof.
FIG. 1 shows a conventional push bar-type ratchet wrench 10 including an elongated stem 11, a ratchet 14 rotatably received in a through hole of the head section 12 of the stem 11 for fitting with a nut and a push bar 16 which is a solid bar with circular cross-section. Each of two ends of the push bar 16 is formed with a detent section 17. The push bar 16 is slidably fitted in a slide way 13 of the head section 12 and pressed by a resilient member 18, whereby the push bar 16 can be located at two positions where the detent section 17 on right side or left side is engaged with the ratchet 14 to provide one-way ratchet effect in different directions.
The conventional push bar-type ratchet wrench can hardly bear high torque and has some shortcomings in operation as follows:
As shown in FIG. 1, when counterclockwise wrenching the stem 11, the ratchet 1 is engaged with the detent section 17 of the push bar for driving the ratchet to rotate in the same direction. At this time, at the contact position A, the detent section 17 will exert a tangential application force F onto the teeth of the ratchet 14. The longitudinal component of the force Fy is directed to the ratchet at a position near the center thereof. The ratchet is a hollow structure and has relatively poor structural strength. Therefore, once the application force F reaches a certain value which makes the longitudinal component of the force Fy greater than the bending strength of the ratchet, the ratchet will be deformed and damaged and unable to be further used.
In addition, referring to FIG. 2, in the operation of FIG. 1, the ratchet 14 will exert a reaction force Fxe2x80x2 onto the push bar 16. The push bar 16 is a solid structure so that it is able to bear the longitudinal component of the force Fyxe2x80x2. However, in the case of excessively great transverse component of the force Fxxe2x80x2, the push bar will clog in the slide way 13 and make it impossible to further use the ratchet wrench.
Furthermore, when clockwise wrenching the wrench as shown in FIG. 3, the push bar 16 will be pushed rightward by the ratchet 14 and disengaged from the ratchet to provide a ratchet effect. The contact position A and the axis of the stem contain a relatively small angle xcex8. Therefore, when the slope face s of the tooth 141 of the ratchet pushes the detent section 17, as shown in FIG. 4, the perpendicular component n2 of the application force N is applied to the push bar 16 to press the push bar 16 against the inner wall of the slide way 13. Therefore, a larger frictional coefficient between the push bar and the inner wall is produced and the ratchet must exert a greater force onto the push bar for transversely pushing the same. As a result, the ratchet effect is insensitive.
In the other types of ratchet wrenches 19 as shown in FIGS. 5 and 6, the ratchets 191 and the detents 192 also have the same shortcomings.
Another conventional ratchet wrench 15 as show in FIGS. 7 and 8, including a push bar 153 slidably fitted in a slide way 152 of a stem 151. Said push bar has a rectangular cross-section and has a detent section 154 formed at one end of which, said detent section 154 is engaged with a ratchet 155. The engagement position B and the axis of the stem 151 contain a small angle xcex8, so that the wrench 15 also have the same shortcomings.
It is therefore a primary object of the present invention to provide a push bar-type ratchet wrench with high torque strength, which is able to bear higher torque.
It is a further object of the present invention to provide the above push bar-type ratchet wrench in which the ratchet can be more sensitively operated.